Hair styling device with power electronic converter

Abstract

A hair styling device includes a heater having at least one heating element. The sensing circuit determines a voltage of the mains supply and outputs a signal indicative of the determined voltage. The power electronic converter converts a mains power supply to a heater drive signal for driving the heater in dependence at least in part on the signal.

Description

Technical Field

[0001] The present invention relates to a hair styling device that utilizes heat and optionally moving air to dry and / or style hair. Background Art

[0002] Hair styling appliances such as hair dryers and hair straighteners utilize heat to allow styling of a user's hair. For example, a hair dryer heats the air that blows out of a nozzle and directs it onto the hair to be dried / styled. A hair straightener heats one or more plates that are arranged to allow a hair strand to be pulled tight and passed through the plate(s) to straighten the hair strand.

[0003] It is desirable that the hair styling appliance be able to be used in regions with different mains voltages. For example, the switch may allow the user to place the hair styling appliance in a low voltage (e.g. nominally 120 Vac) or high voltage (e.g. nominally 230 Vac) mode, depending on the local mains voltage. Summary of the invention

[0004] According to a first aspect, there is provided a hair styling device comprising:

[0005] a heater comprising at least one heating element;

[0006] a sensing circuit for determining a voltage of the mains power supply and outputting a signal indicative of the determined voltage; and

[0007] A power electronic converter is provided for converting the mains power supply into a heater drive signal for driving the heater at least partly dependent thereon.

[0008] By relying on this signal to control the output of the power electronic converter, user errors in selecting the regional voltage can be avoided.

[0009] The hair styling appliance may comprise a heating element drive circuit for generating a further drive signal for driving at least one of the at least one heating element, the heating element drive circuit not forming part of the power electronic converter.

[0010] The heating element drive circuit and the power electronic converter may be configured and connected to drive different groups of heating elements.

[0011] The power electronic converter may be configured to output a fixed output voltage for a range of mains supply voltages. This may allow the hair styling appliance to operate reliably over a range of mains supply voltages. In this context, a "fixed output voltage" includes a DC voltage with little or no voltage ripple, as well as a varying voltage with a fixed average or RMS voltage. For example, the output may be AC ​​or DC with a ripple of up to 100%, depending on the filter (if any) at the output of the electronic power converter.

[0012] The output voltage of the power electronic converter may vary depending at least in part on the currently selected mode or setting of the hair styling appliance. This may allow heater control without the need for current regulating components such as TRIACS.

[0013] The power electronic converter may be an AC to DC converter, or an AC to AC converter.

[0014] The power electronic converter may be a buck-boost converter, a buck converter, a boost converter or any other form of power electronic converter.

[0015] The hair styling appliance may comprise a power factor correction circuit for power factor correction of the power electronic converter and associated load(s).

[0016] The hair styling appliance is capable of accepting a mains power supply having an AC voltage of 85 Vac to 264 Vac.

[0017] According to a second aspect, there is provided a method of controlling power output of a hair styling appliance, comprising:

[0018] a heater comprising at least one heating element; and

[0019] A power electronic converter, used for converting the mains power into a heater driving signal for driving the heater;

[0020] The method includes:

[0021] determining the voltage of the mains power supply to which the hair styling appliance is connected; and

[0022] The power electronic converter is controlled at least in part dependent upon the determined voltage.

[0023] The hair styling appliance may comprise a heating element drive circuit which does not form part of the power electronic converter, and the method may comprise generating, with the heating element drive circuit, a further drive signal for driving at least one of the at least one heating element.

[0024] The method may include driving different groups of heating elements using a heating element drive circuit and a power electronic converter.

[0025] Controlling a power electronic converter may include outputting a fixed output voltage for a range of input voltages. In this context, a "fixed output voltage" includes a DC voltage with little or no voltage ripple, as well as a varying voltage with a fixed average or RMS voltage. For example, the output may be AC ​​or DC with a ripple of up to 100%, depending on the filter (if any) at the output of the electronic power converter.

[0026] Controlling the power electronic converter may comprise varying an output voltage of the power electronic converter at least partly in dependence on a currently selected mode or setting of the hair styling appliance.

[0027] The method may include converting mains power to an AC heater drive signal using a power electronic converter.

[0028] The method may comprise converting the mains power supply into a DC heater drive signal using a power electronic converter.

[0029] The method may include power factor correcting the power electronic converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to make the present invention more easily understood, the embodiments of the present invention will be described below by way of examples in conjunction with the accompanying drawings, in which:

[0031] FIG1 is a schematic diagram showing a hair styling device;

[0032] Figure 2 A schematic diagram showing another hair styling device;

[0033] Figure 3 is a schematic diagram showing a hair styling device in the form of a hair dryer; and

[0034] Figure 4 is a schematic diagram showing a hair styling device in the form of a hair straightener;

[0035] Figure 5 is a flow chart illustrating a method of controlling the power output of a hair styling device;

[0036] Figure 6 Included are three graphs showing various levels of DC ripple in different implementations of AC to DC power electronic converters; and

[0037] Figure 7 is a schematic diagram of an alternative embodiment including a heating element driving circuit. DETAILED DESCRIPTION

[0038] With reference to the accompanying drawings, in particular Figure 1, which shows a hair styling device 100. The hair styling device 100 may take any suitable form, such as a hair dryer, a hair straightener, a curling iron, or any other device that uses heat to dry, style, or straighten hair.

[0039] The hair styling appliance 100 includes a heater in the form of a resistive heating element 102. The heating element 102 may be a high resistance alloy such as a nickel-chromium alloy, in the form of, for example, one or more wires, strips or traces, which may be mounted on or supported by a suitable substrate such as a ceramic former or a PCB. Two or more heating elements may be provided in series, in parallel or in some combination to achieve the desired current and power ratings within the expected operating voltage range.

[0040] The hair styling appliance 100 comprises a sensing circuit in the form of a voltage sensor 104, which is connected between input terminals 106 and 108. When the hair styling appliance 100 is plugged into a mains power supply (not shown), the input terminals 106 and 108 are provided with a mains supply voltage. Depending on the geographical region, the mains supply voltage may be nominally 120 VAC (e.g., in North America) or nominally 230 VAC (e.g., in Europe). Other nominal mains supply voltages, such as, for example, 110 Vac, 220 Vac and 240 Vac may also be suitable.

[0041] Although described as being connected between input terminals 106 and 108, voltage sensor 104 may be connected and configured to determine the voltage at any suitable point in hair styling appliance 100. For example, where a voltage conversion circuit (not shown) is used, the voltage may be determined at the output of the circuit. Such a voltage conversion circuit may include, for example, a voltage divider (providing a scaled output voltage), a passive bridge rectifier, or an active bridge rectifier.

[0042] This signal is supplied by the voltage sensor 104 to the controller 110. In dependence on this signal, the controller 110 outputs a control signal to a power electronic converter 112. The power electronic converter 112 is configured to convert the mains power into a heater drive signal for driving the heating element 102.

[0043] The voltage sensor 104 is configured to determine the mains supply voltage at the input terminals 106 and 108, and output a signal indicating the voltage. The signal can take any suitable form. For example, the signal can be an analog voltage, which can be converted to a numerical value by an analog-to-digital converter, which can form part of the controller 110, or can be a separate circuit. Alternatively, the signal can be a numerical value that can be directly read by the controller 110.

[0044] In other embodiments, the signal may be used directly without conversion to a numerical value, for example by taking the form of a variable voltage that directly controls one or more other elements of the power electronic converter.

[0045] In the hair styling appliance 100, the power electronic converter 112 is configured to output an AC heater drive signal for driving the heating element 102. The power electronic converter 112 may take the form of a controllable AC buck-boost converter, for example. The circuit details and operating principle of the AC buck-boost converter are well known to those skilled in the art and will not be described in detail. However, depending on the implementation requirements, a buck converter, a boost converter or any other form of power electronic converter may also be used.

[0046] The controller 110 controls the output of the power electronic converter 112 based on the signal. Figure 1 In an embodiment, the power electronic converter 112 is controlled to output a fixed AC voltage. The AC voltage is selected to suit the specific implementation requirements, including factors such as component and conductor current ratings, insulation, heating element specifications, etc.

[0047] The fixed AC voltage causes AC current to flow through the heating element 102, causing the heating element 102 to become hotter. The heat from the heating element 102 can be used to heat the air (e.g., in the case of a hair dryer) or the plates (e.g., in the case of a hair straightener). Other hair styling appliances may use heat differently.

[0048] "Fixed output voltage" includes a varying voltage that has a fixed average or RMS voltage. This includes AC voltages and DC voltages that have a large amount of ripple.

[0049] Thus, the hair styling appliance 100 may be plugged into a mains power socket outlet without having to manually select an operating voltage for the hair styling appliance 100 .

[0050] Optionally, the hair styling appliance 100 may include a power factor correction circuit 114 for power factor correction of the power electronic converter and the associated load(s). Power factor correction circuits are known from other unrelated technical fields and are therefore not described in detail.

[0051] Alternatively, the hair styling appliance 100 may be configured such that the output voltage of the power electronic converter 112 varies at least partially in dependence on the currently selected mode or setting of the hair styling appliance 100 .

[0052] For example, the hair styling appliance 100 may provide two or more user-selectable modes, each mode having a different temperature or power requirement for the heating element 102. The power electronic converter 112 may be controlled by the controller 110 such that the power electronic converter 112 outputs a lower voltage in a mode having a relatively lower temperature or power requirement and outputs a higher voltage in a mode having a relatively higher temperature or power requirement. In this way, the temperature or power of the heating element 102 may be controlled without the need for additional power modulation components (such as TRIACS or other power switches).

[0053] The power electronic converter 112 may include, for example, a buck-boost converter, but may also take any other suitable form of power electronic converter to suit a particular implementation.

[0054] See also Figure 2 , which shows an alternative hair styling device 200. The hair styling device 200 shares several components with the hair styling device 100 and is Figure 1 and Figure 2 Like parts are indicated by like reference numerals. The phrase "similar parts" as used here and elsewhere in this specification does not mean that parts with like reference numerals are identical. For example, a heating element of a hair dryer may have a different form and be more powerful than a heating element of a hair straightener, but both are similar parts because they are both heating elements that perform a heating function.

[0055] The power electronic converter 112 of the hair styling appliance 100 outputs AC. In contrast, the hair styling appliance 200 comprises a power electronic converter 116 configured to output DC.

[0056] As with the power electronic converter 112 , the power electronic converter 116 may be configured to output a fixed output voltage for a range of input mains supply voltages, although the fixed output voltage is a DC voltage rather than an AC voltage.

[0057] Again, a "fixed output voltage" includes a fixed average or RMS voltage, which in this embodiment is a DC voltage. The DC voltage may have little or no voltage ripple, or may have up to 100% ripple, depending on the filter (if any) at the output of the electronic power converter. For example, Figure 6 As shown, the power electronic converter can output a DC voltage with 100% ripple as shown in the first graph 160, a DC voltage with about 50% ripple as shown in the second graph 162, or a DC voltage with almost no ripple as shown in the third graph 164. In each case, the power electronic converter outputs a fixed (RMS) voltage.

[0058] Alternatively, the power electronic converter 116 may be configured to output a variable voltage. For example, the hair styling appliance 200 may provide two or more user-selectable modes, each mode having a different temperature or power requirement for the heating element 102. The power electronic converter 116 may be controlled by the controller 110 such that the power electronic converter 116 outputs a lower voltage in a mode having a relatively lower temperature or power requirement and outputs a higher voltage in a mode having a relatively higher temperature or power requirement. In this way, the temperature or power of the heating element 102 may be controlled without the need for additional power modulation components such as field effect transistors.

[0059] In hair styling appliances 100 and 200, power electronic converters 112 and 116 are both capable of accepting a mains power supply having an AC voltage of 85 VAC to 264 VAC. However, those skilled in the art will appreciate that power electronic converters having different input voltage operating ranges may be used in other embodiments.

[0060] Go to Figure 3 , a hair styling device in the form of a hair dryer 300 is shown. The hair dryer 300 shares several components with the hair styling devices 100 and 200 and is Figure 1 , Figure 2 and Figure 3 The same components are denoted by the same reference symbols.

[0061] The hair dryer 300 includes a handle 118 connected to a tubular body 120. The body 120 defines an airflow path 122 in which a fan unit 124 is disposed, the fan unit including a motor 126 and an impeller 128 connected to be driven by the motor 126. The heating element 102 is disposed in the airflow path 122 downstream of the fan unit 124.

[0062] The handle 118 houses the voltage sensor 104, the controller 110, and the power electronic converter 112. The handle 118 houses a motor driver 130 configured to drive the fan unit 124 according to a drive signal received from the controller 110. The handle 118 also houses a heater driver 132, which includes a TRIAC (not shown). The TRIAC is connected to receive the AC output of the power electronic converter 112 and modulate the AC output according to a heater control signal from the controller 110.

[0063] The controller 110 may use, for example, a burst trigger control scheme (a combination of half and / or full power cycle conduction time periods, with possible gaps between conductions), a phase control scheme (partial conduction cycle, typically by varying the conduction start point), a combination of the above schemes, or any other suitable control scheme for controlling a TRIAC. TRIAC control schemes are well known to those skilled in the art and will not be described in detail.

[0064] The user interface 138 is disposed on the handle 118 and includes, for example, a switch (not shown) that enables the user to select one of three heating modes: off, low power, and high power. In the "off" mode, no power is supplied to the heating element 102, so the air blown by the fan unit 124 is not significantly heated when it leaves the body 120 (the air cooling motor 126 may cause some slight heat increase).

[0065] Other user interface elements may be used as an alternative or in addition to switches. For example, one or more dials, sliders, buttons, touch surfaces, or other input elements may be provided as part of the user interface. The user interface may also provide feedback through one or more screens, lights, sounds, etc.

[0066] In the "low power" mode, the controller 110 controls the heater driver 132 so that the TRIAC conducts for approximately half a cycle (on average), resulting in the heating element 102 outputting approximately half of the power available from the power electronic converter 112. In the "high power" mode, the controller 110 controls the heater driver 132 so that the TRIAC conducts continuously, resulting in the heating element 102 outputting the full power available from the power electronic converter 112.

[0067] In other implementations, any number of heater settings may be provided for user selection via a user interface, with each heater setting having a suitable heater power output or temperature.

[0068] The speed of the fan unit 124 may also be controlled according to a mode or setting selected by a user via the user interface 138. The fan speed may be a separate setting, or may form an element of a mode including, for example, a fan speed setting and a heater setting.

[0069] A mains power cable 134 extends from the handle 118 and terminates in a mains power plug 136. The plug 136 is configured to comply with applicable standards in the region in which the hair dryer 300 is to be used. The other end of the cable 134 provides mains power to the internal components of the hair dryer 300.

[0070] In an alternative embodiment, the sensing circuit can indirectly identify the mains voltage. For example, the electrical plug may include an ID component configured to provide an ID data item. The sensing circuit includes a configuration to read the ID component, wherein the controller is operable to determine the mains voltage associated with the electrical plug by means of the ID component.

[0071] The electrical plug may include a plug body and a detachable plug terminal, the plug body including the sensing circuit. By providing different plug terminal types for different countries' plug / socket standards, the hair styling appliance is able to determine the mains voltage based on which plug terminal is connected to the plug body. For example, a UK plug type indicates that 240V mains is expected, while a US plug type indicates that 120V mains is expected.

[0072] The plug body may be integrated into the body of the hair styling appliance. However, in other embodiments, the plug body may be located at the end of an electrical cable extending from the body of the hair styling appliance.

[0073] The ID component and the ID reader can take a variety of forms. For example, the ID reader can be a vision-based system that is configured to recognize a certain type of visual mark or logo that constitutes the ID component. In other examples, the ID component can be a series of bumps or protrusions, similar to the Braille system, which are configured to represent data items. Similarly, the ID reader can include a microswitch array that is configured to detect the ID data item in response to the array of protrusions.

[0074] In a particularly flexible example, the ID component is a data processing component, such as an RFID transponder / tag, which is configured to transmit an ID data item to an ID reader, which may be constituted by an RFID receiver. The ID component may be configured to store and transmit manufacturer-defined data to the ID reader, thereby allowing the mains voltage to be identified. This may be direct (i.e., the mains voltage is sent in numerical form) or indirect (i.e., the ID component identifies the country, plug terminal or other information, based on which the hair styling appliance can look up the corresponding mains voltage).

[0075] The ID reader may be located at the plug body. However, this is not essential and it is envisaged that the ID reader may be located elsewhere on the hair styling appliance, for example on the main body. The location of the ID reader may depend on various factors. Placing the ID reader on the plug body, close to the plug terminals, means that relatively low powered RFID tags may be used, such as passive tags capable of operating over short transmission distances. So-called 'active' RFID tags have their own power source, rather than drawing power from the RFID transceiver as passive tags do, and therefore have the ability to transmit over longer distances, making them suitable for use in hair styling appliances where a greater distance between the ID component and the ID reader is required.

[0076] In an alternative embodiment, the hair dryer 300 may omit the heater driver 132. In one such embodiment, the heating element 102 is driven only at a single fixed power, which is determined by the output voltage of the power electronic converter 112. The temperature of the heated air output from the hair dryer 300 is in turn dependent on the power and the airflow rate.

[0077] In another such embodiment, the output voltage of the power electronic converter 112 may be controlled by the controller 110, as described above with respect to Figure 1 The output temperature of the heated air output from the blower 300 in turn depends on the voltage output by the power electronic converter 112 and the air flow rate.

[0078] Go to Figure 4 , a hair styling device in the form of a hair straightener 400 is shown. The hair straightener 400 shares several components with the hair styling devices 100, 200 and 300 and is Figure 1 , Figure 2 , Figure 3 and Figure 4 Similar components are denoted by the same reference symbols.

[0079] The hair straightener 400 includes a handle 140 in which a voltage sensor 104 , a controller 110 , and a power electronic converter 116 are disposed.

[0080] The hair straightener 400 includes a first arm 142 and a second arm 144. The first arm 142 and the second arm 144 are connected to the handle 140 at a hinge 146 so that the arms can pivot away from each other.

[0081] The first arm 142 includes a first plate 148 and the second arm 144 includes a second plate 150. The first plate 148 and the second plate 150 are formed of a thermally conductive material and may include a non-stick coating. Optionally, one or both of the first plate 148 and the second plate 150 may be flexible along their length to conform to and apply pressure to the hair clamped therebetween when the hair straightener 400 is in use.

[0082] The hair straightener 400 includes two heating elements 102 , each positioned along one of the first plate 148 and the second plate 150 .

[0083] A spring (not shown) biases the arms away from each other so that a user can place a strand of hair between the first plate 148 and the second plate 150 and then squeeze the first arm 142 and the second arm 144 together to capture the strand of hair between the first plate 148 and the second plate 150 .

[0084] In contrast to the hair dryer 300 , the hair straightener 400 does not include any form of heater driver between the power electronic converter 116 and the heating element 102 . Instead, the heating element 102 is driven directly by the power electronic converter 116 .

[0085] In one embodiment, the output voltage of the power electronic converter 116 of the hair dryer 300 can be controlled by the controller 110, as described above with respect to Figure 2 The temperature of the first plate 148 and the second plate 150 in turn depends on the voltage output by the power electronic converter 116 and the heat loss from the hair and the surrounding environment.

[0086] In another embodiment, the heating element 102 of the hair dryer 300 is driven at a single fixed power determined by the fixed output voltage of the power electronic converter 116. The temperature of the first plate 148 and the second plate 150 in turn depends on the output voltage and the heat loss of the hair and the surrounding environment.

[0087] Although hair dryer 300 has been described as using power electronic converter 112 (AC to AC) and hair straightener 400 has been described as using power electronic converter 116 (AC to DC), those skilled in the art will appreciate that either type of power electronic converter may be used in any hair styling device application.

[0088] In addition, the AC or DC output of a power electronic converter can have its average or RMS voltage controlled by various modulation schemes including burst triggering, phase control, pulse width, etc.

[0089] The use of variable voltage output power electronic converters in relatively low power applications may provide particular advantages. In this article, "low power" means having an average output power of less than about 500W, although in other approaches, "low power" means having an average output power of less than about 400W, 250W, or even 200W.

[0090] For example, many hair dryers have relatively high heat output requirements, sometimes exceeding one kilowatt. In at least some embodiments, such high power requirements can make it expensive to provide a variable voltage output power electronic converter. On the other hand, the lower heat output requirements of a typical hair straightener can make the use of a variable voltage output power electronic converter more desirable.

[0091] Although a "buck-boost" power electronic converter has been mentioned, it will be appreciated by those skilled in the art that other forms of power electronic converters may also be used. For example, a power electronic converter that only steps down or steps up the input mains supply voltage may be used. Other forms of voltage increasing and / or decreasing circuits may also be used.

[0092] Any suitable type of controller may be used. For example, controller 110 may employ a microprocessor (with associated support circuitry, if desired), a microcontroller, or any suitable combination of analog and / or digital hardware and / or software.

[0093] For the sake of clarity, Figures 1 to 4 Some non-critical implementation details are omitted. For example, the controller 110 may require a DC power source, but this is omitted from the figure to avoid unnecessary clutter. One or more temperature sensors may be used to control the temperature of any or all of the heating elements, the air heated by the one or more heating elements, the components heated by the one or more heating elements (e.g., the plates in a hair straightener), the ambient temperature, any other temperature, or any combination thereof.

[0094] Those skilled in the art will appreciate that all drawings are schematic in nature and are not drawn to scale. Figure 4 and Figure 5 , the locations of specific components within the hair styling appliance are exemplary only and may vary depending on the implementation.

[0095] For example, although user interface 138 is schematically shown as a single component located in / on handle 118, user interface 138 may alternatively be located elsewhere in / on the hair styling device, including distributed at different locations in / on the hair styling device. Similar descriptions apply to other components.

[0096] One or more components of the hair styling appliance may be located in a separate housing. A mains power cable 134 is connected to the separate housing. Another electrical cable (not shown) connects the separate housing to the hair styling appliance. For example, a component such as the motor drive 130 may be located in a separate housing. In this case, the other cable carries power for the hair styling appliance, as well as the motor drive signal from the motor drive 130. One or more other components of the hair styling appliance, such as the controller 110 (or a sub-controller or circuit forming part of the controller 110) or the power electronic converter 116, may also be contained in a separate housing.

[0097] Go to Figure 7 , an alternative embodiment of a hair styling appliance 166 is shown. The hair styling appliance 166 includes a heating element drive circuit 168 and a further heating element 170.

[0098] The heating element drive circuit 168 is controlled by the controller 110 and is configured to generate additional drive signals for driving the additional heating elements 170. The heating element drive circuit 168 and the power electronic converter 112 are configured and connected to drive different groups of heating elements. The heating element drive circuit 168 does not form part of the power electronic converter 112.

[0099] The heating element drive circuit 168 may include any suitable circuit to generate an additional drive signal for the heating element 170. For example, the heating element drive circuit 168 may include one or more switching elements or circuits, such as TRIACS, MOSFETs, relays, etc., which are controlled by the controller 110 to drive the heating element 170 as needed. The heating element drive circuit may also take the form of an additional power electronic converter. The additional drive signal may be AC ​​or DC, including power modulated AC or DC.

[0100] Although the heating elements 102 and 170 of the hair styling appliance 166 are connected to be driven individually by the power electronic converter 112 and the heating element drive circuit 168, respectively, those skilled in the art will appreciate that in other embodiments, the heating elements may be connected such that at least one of them may be driven by both the heating element drive circuit and the power electronic converter.

[0101] Go to Figure 5 , a method 152 of controlling the power output of a hair styling appliance is shown. The method 152 may be performed by a controller, such as the controller 110 described above. The method may be embodied in analog or digital hardware, firmware or software, or any combination thereof.

[0102] The hair styling appliance may comprise a heater comprising at least one heating element and a power electronic converter for converting supplied mains power into a heater drive signal for driving the heater.

[0103] The method 152 comprises determining 154 a voltage of a mains power source to which the hair styling appliance is connected, and controlling 156 a power electronic converter at least partly in dependence on the determined voltage.

[0104] Step 156 may optionally include outputting a fixed output voltage for a range of different input voltages.

[0105] Alternatively, step 156 may optionally include varying the output voltage of the power electronic converter depending at least in part on a currently selected mode or setting of the hair styling appliance.

[0106] Step 156 may include converting the mains power to an AC heater drive signal or a DC heater drive signal using a power electronic converter.

[0107] Optionally, the method 152 may include power factor correcting the power electronic converter.

[0108] Although the sensing circuit has been described as a voltage sensor, a person skilled in the art will appreciate that the term "sensing circuit" is used broadly. In the context of the present application, "sensing circuit" includes any combination of circuits and / or components that output one or more signals that are directly or indirectly indicative of the voltage of the mains power supply to which the hair styling appliance is or is to be connected.

[0109] The use of signals "indicating" voltage is also extensive, including direct indication and indirect indication. "Direct indication" includes, for example, the arrangement of an analog or digital signal that the sensing circuit outputs to indicate a specific mains voltage or voltage range. "Indirect indication" means that the output of the sensing circuit depends on the mains voltage, but does not directly represent the mains voltage. For example, the sensing circuit can measure the current at a specific point, which varies according to the mains voltage. The sensing circuit can measure the temperature of a specific component or multiple components, where the temperature varies based on the mains voltage. There is no need to explicitly convert the current or temperature signal into a voltage before using it.

[0110] Although the invention has been described with reference to various embodiments, it will be appreciated by those skilled in the art that the invention can be embodied in many other forms and is limited only by the scope of the claims.

Claims

1. A hair styling device comprising: a heater comprising at least one heating element; a sensing circuit for determining a voltage of a mains power source and outputting a signal indicative of the determined voltage; as well as A power electronic converter for converting the mains power supply into a heater drive signal for driving the heater at least partly dependent on said signal.

2. A hair styling appliance according to claim 1, comprising a heating element drive circuit to generate a further drive signal for driving at least one of the at least one heating element, the heating element drive circuit not forming part of the power electronic converter.

3. A hair styling appliance according to claim 2, wherein the heating element drive circuit and the power electronic converter are configured and connected to drive different groups of the heating elements.

4. A hair styling appliance according to any preceding claim, wherein the power electronic converter is configured to output a fixed output voltage for a range of mains supply voltages.

5. A hair styling appliance according to claim 1, configured such that the output voltage of the power electronic converter varies at least partly in dependence on a currently selected mode or setting of the hair styling appliance.

6. A hair styling appliance according to any preceding claim, wherein the power electronic converter is an AC to DC converter.

7. A hair styling appliance according to any one of claims 1 to 5, wherein the power electronic converter is an AC to AC converter.

8. The hair styling appliance of claim 1, wherein the power electronic converter is a buck converter, a boost converter, or a buck-boost converter.

9. A hair styling appliance according to any preceding claim, comprising a power factor correction circuit for power factor correction of the power electronic converter and associated load(s).

10. A hair styling appliance according to any preceding claim, wherein the power electronic converter is capable of accepting a mains power supply having an AC voltage of 85 VAC to 265 VAC.

11. A method of controlling the power output of a hair styling device, comprising: a heater comprising at least one heating element; as well as A power electronic converter for converting a mains power supply into a heater drive signal for driving the heater; The method comprises: determining the voltage of a mains power source to which the hair styling appliance is connected; and The power electronic converter is controlled at least in part dependent upon the determined voltage.

12. A method according to claim 11, wherein the hair styling appliance comprises a heating element drive circuit which does not form part of the power electronic converter, the method comprising generating, using the heating element drive circuit, a further drive signal for driving at least one of the at least one heating element.

13. A method according to claim 12, comprising driving different groups of the heating elements using the heating element drive circuit and the power electronic converter.

14. The method of any one of claims 11 to 13, wherein controlling the power electronic converter comprises outputting a fixed output voltage for a range of input voltages.

15. The method of claim 11, wherein controlling the power electronic converter comprises varying an output voltage of the power electronic converter at least partially dependent on a currently selected mode or setting of the hair styling appliance.

16. A method according to any one of claims 11 to 15, comprising converting the mains supply to an AC heater drive signal using the power electronic converter.

17. A method according to any one of claims 11 to 15, comprising converting the mains supply into a DC heater drive signal using the power electronic converter.

18. A method according to any one of claims 11 to 17, comprising applying power factor correction.

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